Interaction of the cotranslational Hsp70 Ssb with ribosomal proteins and rRNA depends on its lid domain

• Published in: Nature communications Vol. 7; no. 1; pp. 13563 - 12
• Main Authors: Gumiero, Andrea, Conz, Charlotte, Gesé, Genís Valentín, Zhang, Ying, Weyer, Felix Alexander, Lapouge, Karine, Kappes, Julia, von Plehwe, Ulrike, Schermann, Géza, Fitzke, Edith, Wölfle, Tina, Fischer, Tamás, Rospert, Sabine, Sinning, Irmgard
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.11.2016; Nature Publishing Group; Nature Portfolio
• Subjects: 631/337/574/1789; 631/45/470/1981; 631/535/1266; 82; 82/83; Adenosine diphosphate; Adenosine Diphosphate - metabolism; Adenosine Triphosphate - metabolism; ATP; Biochemistry; Crystallography, X-Ray; GTP-Binding Proteins - metabolism; GTP-Binding Proteins - ultrastructure; HSP70 Heat-Shock Proteins - metabolism; HSP70 Heat-Shock Proteins - ultrastructure; Humanities and Social Sciences; multidisciplinary; Peptide Elongation Factors - metabolism; Peptide Elongation Factors - ultrastructure; Polypeptides; Protein Conformation, alpha-Helical; Proteins; Ribonucleic acid; Ribosomal Proteins - metabolism; RNA; RNA, Ribosomal - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins - metabolism; Saccharomyces cerevisiae Proteins - ultrastructure; Science; Science (multidisciplinary); Yeasts; Germany
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms13563

Cotranslational chaperones assist in de novo folding of nascent polypeptides in all organisms. In yeast, the heterodimeric ribosome-associated complex (RAC) forms a unique chaperone triad with the Hsp70 homologue Ssb. We report the X-ray structure of full length Ssb in the ATP-bound open conformation at 2.6 Å resolution and identify a positively charged region in the α-helical lid domain (SBDα), which is present in all members of the Ssb-subfamily of Hsp70s. Mutational analysis demonstrates that this region is strictly required for ribosome binding. Crosslinking shows that Ssb binds close to the tunnel exit via contacts with both, ribosomal proteins and rRNA, and that specific contacts can be correlated with switching between the open (ATP-bound) and closed (ADP-bound) conformation. Taken together, our data reveal how Ssb dynamics on the ribosome allows for the efficient interaction with nascent chains upon RAC-mediated activation of ATP hydrolysis. In yeast, the heterodimeric ribosome-associated complex (RAC) acts in concert with the Hsp70 protein Ssb, forming a unique chaperone triad. Here the authors use structural and biochemical approaches to shed light on how translation and folding are coupled in eukaryotes.